The present embodiments relates to an electron gun.
An electron gun generally has a cathode for emitting free electrons, which are subsequently accelerated by an electron-optical system. Devices that concentrate the electrons to form a directional beam and focus the directional beam onto a target region may also be present. By way of example, electrostatic lenses or magnetic fields are used for this purpose. In the case of electron beams of high current density, the minimum achievable focus size is emitted by the mutual repulsion of the electrons within the beam.